1. Field of the Invention
The present invention relates to the manufacturing method of a laminated magnet film end product with self-bonding layer that is mainly applied to the rotor of minute rotary electrical machines.
2. Description of the Related Art
Considering miniaturization and weight saving of rotary electrical machines, for example, the rotary electrical machines in the field of information and communication devices, the market expects the rotary electrical machines to be miniaturized and weight-saved up to approximately 40 mm3 in their volumes and 300 mg in their weights. In the torque of these rotary electrical machines, power approximation is established based on a scaling law in the relation of the volume of the rotary electrical machines, thereby causing considerable torque deteriorations. Accordingly, in the rotary electrical machines applied as a driving force of advanced electrical-and-electric equipments in fields of vehicles, information home appliances, communication instruments, precision measuring devices, medical-and-welfare equipments, or robots, torques improvement has been strongly demanded.
For example, Patent Application Publication H09-501820 (Patent Document 1) discloses an intravascular ultrasonic-scanning system for radially air-gap type DC brushless motors with their outer diameters of 1 mm or less and their lengths of 2 mm or less. In the system, a cylindrical main body that has a conductive cylindrical wall with a slot is applied as an excitation winding.
In the minute rotary electrical machines as discussed hereinabove, for example, a Nd2Fe14B sintered magnet that has been subjected to electrical discharge machining to form a predetermined shape is magnetized with single pole pair in a radial direction of an outer diameter of 0.76 mm. The rotor of an anisotropic bulk magnet is thus obtained. This rotor is then combined with a stator core so as to obtain a rotary electrical machine (DC brushless motor) having the outer diameter of 1.6 mm and the length of 2 mm. See Non-patent document 1. Further, by using the rotor of the anisotropic bulk magnet as discussed hereinabove, H. Raisigel, M. Nakano or Itoh et al. respectively introduce minute rotary electrical machines with the outer diameter of 6 mm and the length of 2.2 mm (see Non-patent Document 2), with the outer diameter of 5 mm and the length of 1 mm (see Non-patent document 3) and with the outer diameter of 0.8 mm and the length of 1.2 mm (see Non-patent document 4).
As regards the rotor of the anisotropic bulk magnet as explained above, for example, an anisotropic Nd2Fe14B based sintered magnet is ground so as to make its outer diameter to be 0.9 mm. The surface of the magnet is formed with a sputtering layer such as Dy, Tb. The magnet is then subjected to heat treatments for inducing the internal diffusion thereof so as to achieve surface modification. Accordingly, its remanence Mr of the magnet reaches to 1.35 T while its coercivity HcJ recovers up to 1.34 MA/m. Further, its (BH)max reaches to 341 kJ/m3. See Japanese Patent Application Laid-open 2005-210876 (Patent Document 2).
Considering an anisotropic magnetic film, not like the anisotropic bulk magnet discussed hereinabove, D. Hinz et al. introduce a magnetic film that has the thickness of 300 μm, the magnetic film being produced by a die upset method at the temperature of 750° C. This anisotropic magnetic film has the remanence Mr of 1.25 T, the coercivity HcJ of 1.06 MA/m, and the (BH)max of 290 kJ/m3 in a direction perpendicular to the surface of the magnet film. See Non-patent document 5. It is known that this type of the high remanence Mr typed magnet film is applicable as the rotor of the anisotropic magnet film of rotary electrical machines. See Non-patent document 6.
Töpfer and T. Speliotis et al use a Nd2Fe14B-based bonded magnet film as the rotor of an isotropic magnet film, the bonded magnet film being screen-printed on a Fe—Si plate with its diameter of 10 mm where its remanence Mr is 0.42 T, its (BH)max is 15.8 kJ/m3, and its thickness is 500 μm. Rotary electrical machines (stepping motors) that have the torque of 55 μNm are thus achieved. See Non-patent document 7.
On the other hand, by compression-molding compound composed of a binder and crushed powder of a crystallized rapid-solidified film that is magnetically isotropic, a bonded magnet with the density of 6.0 Mg/m3 that has been subjected to thermal hardening is applied as a rotor that has its diameter of 3 mm and six pole pairs. Here, the above-described crushed powder includes nanocomposites that have the coercivity HcJ of 600 kA/m or more, the remanence Mr of 0.94 T or more, and α-Fe phase and R2Fe14B phase (R is either Nd or Pr) of 60 nm or less. Based on the above, it has been reported that the torque of the rotary electrical machines (the stepping motors) is approximately improved up to 15% compared to the rotor of a Nd2Fe14B single phase bonded magnet that has the density of 6.0 Mg/m3. See Japanese Patent 4089220 (Patent Document 3).
As noted above, when considering magnets applied to the rotor of the minute rotary electrical machines, the wide range of magnetic properties, for example, the remanence Mr of 0.42 T up to 1.35 T) have been examined. In addition, a variety of materials such as powders, films, or bulks have been also examined.
Here, a specific molten alloy that has a compositional formula of Fe100-x-yRxAy (R is at least one of Pr, Nd, Dy, and Tb; A is C or at least one of B; 1 at. %≦x<6 at. %, 15 at. %≦y≦30 at. %) is subjected to specific rapid-solidified treatments so as to obtain a film that has the thickness of 10 μm to 100 μm, and has more than 90% of amorphousness, the film being in excellent tenacious qualities and having elastically deformable capabilities. The film may be used as it is, or may be cut into a predetermined length, or may be die-cut into an optional shape. The film is then subjected to thermal treatments of 550° C. to 750° C. so as to obtain a nanocrystalline structure with Fe3B phase and Nd2Fe14B phase that has an average grain size of 10 nm to 50 nm. Accordingly, a nanocrystalline film is obtained from the amorphous phase where its coercivity HcJ is 160 kA/m or more, and its remanence Mr is 0.8 T or more. At least two of the nanocrystalline films are laminated and adhered to each other by means of epoxy resin. With this method, it would be possible to obtain a high-performable laminated magnet film end product that has optional thickness and desired shape with no grind on films or laminates, or no bonded magnet. See Japanese Patent 3643214 (Patent Document 4).
Further, the following manufacturing method of a laminated magnet has been also known. That is, metal that has a melting point of 200° C. to 550° C. is galvanized or evaporated on the surface of a rapid-solidified film that has the thickness of 10 μm to 100 μm, and that is made of 90% or more of amorphous structures as discussed hereinabove. This rapid-solidified film may be used as it is, or may be processed into a predetermined shape. Then, the rapid-solidified film is laminated and subjected to thermal treatments of 550° C. to 750° C. so as to obtain a nanocrystalline structure with a Fe3B phase, a α-Fe phase, and a Nd2Fe14B phase that has an average grain size of 10 nm to 50 nm. The surface of metal layer of the film is also melted at the same time, so that the laminated films become integrated to each other. This manufacturing method of the laminated magnets is disclosed in Japanese Patent 3643215 (Patent Document 5).
Further, considering Patent Document 6 (Japanese Patent 3886317), a Fe-based magnet with its thickness of 200 μm to 300 μm identifiable by the compositional formula of either Fe100-y-zCo10RyBz or Fe100-y-zCo9.5TM2RyBz is disclosed. In the above formula, TM is an element selectable from at least one of V, Ti Cr, Mn, Cu, Nb, Mo, Wm Ta, Hf and Zr. R is an element selectable from at least one of Nd, Pr. B is boron. And, y and z showing a compositional ratio is 2.5<y<4.0 and 19<z<25 at. %. As to physical properties of the magnet, the temperature interval Δ Tx within undercooled liquid that can be identified by the formula of Δ Tx=Tx−Tg is 35 C.° or more (here, Tx indicates a temperature that crystallization starts, and Tg indicates a temperature of glass transition). Its reduced vitrification temperature that can be determined by the formula of Tg/Tm is 0.55 or more (Tm indicates the melting temperature of alloy). The magnet is obtainable through a single-roll rapid solidification method, the magnet having its thickness of 200 μm to 300 μm. The volume ratio of its amorphous phase of the magnet is 90% or more. In addition, the magnet is alloy where metallic glass alloy is subjected to heat treatments. The alloy is made of a structure composed of R2Fe14B, Fe3B, α-Fe phase, and a remaining amorphous phase where its average grain size is 50 nm or less. The alloy has magnetic properties as that its remanence Mr is 1 T or more, and its coercivity HcJ is 150 kA/m or more.